THE ESSENTIALS IN FERTILISERS.

Waikato Times, Volume XXI, Issue 1734, 16 August 1883, Page 3

THE ESSENTIALS IN FERTILISERS.

Puactick and experiment in the growth of crops have shown that nitrogen, phosphates, potash, .'an'dli]Jn£,''m assimilable form, are the substances which most strikingly benefit land ; and chemical analysis has determined in a^ measure the varying proportions in -which, different crops draw upon these and upon other constituents of the soil. Acting on this knowledge, chemists have given specifications for the preparation of manures for all different ci ops, these schemes being professedly based on the composition of the ciops themselves But manuring on this principle would often cost more than the ' consequent increase of the ciop would repay, for it makes no allowance for natural fertility, and it makes no distinction hetweea the composition of the crops glow n and the composition of the produce sold off the faim. We know that soils are of very unequal fertility, that some have an unlimited food supply compared with othcis, and that it is only tlie matuiials sold o(F the faim that the maintenance of fertility requires to bo restored. Alore than this, crops differ gicatly in their capability of self-supply. Take, as an example) of the latter chaiacteiistic, the relations of wheat and clovei to nitiogen. Chemical analysis shows that clover contains mote nitiogen than wheat; and yet the wheat iinds its nitrogen with difficulty, while the clover seems to have a power of self-supply in this particular. Thus, in de'mnce of the chemical composition of the two crops, the farmer's ' practice, when he mamucs wheat libera'ly with nitrogen and gives little or none to clover, is justified. Economic manuring must supplement the plant's weakness, while it makes good the deticionces of the soil. A general manure contains all the constituents of the crop, or nt least all those in which <*oils an 1 most deficient; but ifc by no nieano follows that e\ei} substance which may act benoh'cilly as a nianuie ought to bo applied. If a .soil it, deficient in one part : cular element, and coutains all the other iequi«itos of fertility, th.it one substance may act as beneficially (when applied as though it weie a m.UHiic containing all the constituents) of the ciop. Thu ci op in tin > c.isu is thiowu upon the natuial icsouiecs of thu '.oil for all its other elements. After a heavy diessing of one substance, that substance may not be lefjuncd foi scveial \cars, but some other substance mny bo needed; and this all the more becau>e the larger ciops now glow 11 will exhaust such otha substances more uipully than the smallei ci ops did pie\iously, ]Jy peisisting in the exclusive use of a special manure an ultimate exhaustion of the soil is inevitable. Judiciously used, special manures aie the agents which biing into useful activity the doim.int resources of the soil ; they icstoie the pioper balance between its diilereut constituents, and supply the excessive demand for home particular elements. Still, the application useful on one soil may be <|iuto useless on another, and the application may be u&eful on a soil in one season and useless in another. A general manure, may be used year after yeai in a peifectly louline m.mncr, but \\ heir a speuiil mannio is employed, the impoitiince of watching its efiects and alteiing it as ciiciunstanocs indicate, cannot be over-estim.iied. Tins ioiccs upon us the necessity for studying the succession of inanities as well as that of crops. In many cases in which ammonia when first used pi oved beucliuil, it now begins to lose its effect and the icason no doubt is, thatbj its means the amount of phosphates existing in these soils have been reduced, w hile the ammonia has accumulated .so that change of manuiiiig is needed,